It is most definitely disputable that it destroy social cohesion. The US was cohesive after WWII, by that point we already had a LOT of non-white people. Also black Americans have been here since the start.
1950 Census
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Race Percentage of Total Population
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White 89.5%
Black 10.0%
Other Races 0.5%
Keep in mind the black population was essentially segregated at this point.
Wrong.
Keep in mind the black population was essentially segregated at this point.